Method and apparatus for sealing cartons



Dec. 7, 1954 P. E. FISCHER 2,696,245

METHQD AND APPARATUS FOR SEALING CARTONS v A rra/Mey Dec. 7, 14954 P. E. FISCHER 2,696,245

METHOD AND APPARATUS FOR SEALING CARTONS Filed Dec. 23, 1950 6 Sheets-Sheet 2 lli/VENTURA'- PAUL E. FSGHER BVM/0%? Arron/vn Dec 7, 1954 P. E. FISCHER 2,696,245

METHOD AND APPARATUS FOR SEALING CARTONS Filed Deo. 23, 1950 6 Sheets-Sheet 3 F7' Fla@ Fi Vl/H30 IN VEN TOR.'-

PAUL E. FISCHER BY ArroNsy Dec. 7, 1954 P. E. FISCHER 2,696,245

METHOD AND APPARATUS FOR sEALING cARToNs I I' IV I* PAUL E, FISCHER www M mmv Dec. 7, 1954 P. E. FISCHER 2,696,245

METHOD AND APPARATUS FOR SEALING CARTONS /NvE/vronf- PAUL E. FISCHER By Arramvfy Dec. 7, 1954 P. E. FISCHER 2,695,245

METHOD AND APPARATUS FOR SEALING CARTONS Filed Dec. 23. -.1.950 6 Sheets-Sheet 6 FIG. l2

United States Patent 'ffice t, p 2,696,245 Patented Dec. 7, 1954 METHOD AND APPARATUS FOR SEALING CARTONS Paul E. Fischer, Minneapolis, Minn., assigner to General Mills, Inc., a corporation of Delaware Application December 23, 1950, Serial No. 206,461

17 Claims. (Cl. 154-42) This invention relates to packaging machinery for closing containers and more particularly to a machine and method for sealing a carton by uniting the top closure elements of the container with a covering closure gn object of the invention is to provide an improved method and mechanism for sealing closed cartons having non-rigid side walls and having a top closing flap with alayer of thermoplastic adhesive on the underside overlying folded and sealed top closure elements, by the application of heat and pressure to seal the` top closing ap over the folded closure elements obtaining a smooth and tight integral seal between the carton and ap without disturbing the folded and sealed underlying closure elements and without deforming the carton side walls.

A further object of the invention is to provide an improved mechanism for receiving a carton having the closing elements folded and for sealing the top closure flap to the carton by simultaneously pressing the ap to the carton and pulling it away from its line of attachment to the carton to provide a smooth uniform integral seal between the ap and the carton.

A further object of the invention is to provide a mechanism which will receive a carton, having its closure elements folded, hold closure elements in closed position while inverting the carton, slide the carton in an inverted position over a heated sealing plate pressing the carton against the plate to seal a top cover flap over the closure elements, and thereafter permit the Ailap to cool while continuing pressure on the ap subsequently discharging the sealed carton.

Other objects and advantages will become apparent from the following specification, taken in connection with the attached drawings, in which:

Figure 1 is a perspective view of the carton sealing machine embodying the features of the present invention and a closing machine from which cartons are received;

Fig. 2 is a perspective view of a carton of the general type which may be sealed by the machine;

Fig. 3 is a rear elevation of the carton sealing machine;

Fig. 4 is a sectional view taken along line 4-4 of Fig. 3;

Fig. 5 is an enlarged fragmentary sectional view showing the position of the carton with respect to the holders:

Fig. 6 is a front elevation of the carton holding deadbox, illustrating in detail the safety cutout switch;

Fig. 7 is an enlarged fragmentary sectional view taken from the rear of the machine showing in detail the manner in which heat and pressure are applied to the carton flap;

Fig. 8 is a fragmentary rear elevation of the mechanism illustrating the manner in which the cartons are removed from the mechanism for inverting them;

Fig. 9 is a sectional view taken along line 9--9,of

Fig. 7, illustrating the carton being slid on the heated anism showing the path of the carton through the mechanism;

Fig. 12 is a plan View pf the mechanism, illustrating the path of the carton with respect to the closing machine with which it may be associated.

The machine illustrated, which embodies the preferred form of the present invention, performs the function of sealing the nal ap of a container after the other closing elements have been folded and sealed. A mechanism for closing the other folding elements may be found in the co-pending patent application, Serial No. 206,464, tiled concurrently herewith, Carton Closing Machine, which constitutes the preferred mechanism for use with the present invention. However, other closing machines may be used. The drawings show schematically in Fig. l, the closing mechanism of the type disclosed in the above-mentioned co-pending application. The closing machine comprises a turret 12 having a series of pockets 13 along the circumference which hold lled cartons. The turret operates in the well known manner, being indexed to carry the cartons through a series of stations. The cartons are received into the turret at the point marked Station R, and at each succeeding station the carton top rcceives an additional folding step by folding devices, not shown, until closed and sealed. The carton is closed and ready for ejection when it reaches the discharge station marked Station D, opposite the sealing machine. lt will be understood that the invention is not to be limited to use with a closing machine of the turret type, but may receive cartons from any machine which satisfactorily completes the series of closing operations.

To distinguish the turret mechanism, which folds and seals the closure elements, from my invention which seals only the top closure ilap, I shall refer to the former as a closing mechanism, and to the present invention as a sealing mechanism. The carton 14 is shown in Fig. 2 as it is received from the closing machine, having a portion of its closure elements folded and sealed but with the top closure ap unsealed.

The carton 14 is preferably a semi-rigid carton, such as may be formed of laminations of thermoplastic adhesive and metallic foil. The top closure ap 16, which lies over the other closure elements 18, is hingedly attached to a side wall 19 of the carton and has a coating 20 on its underside of adhesive, preferably thermoplastic adhesive. Sealing this top flap to the body of the package over the other closing elements completes the closure of the container. It will readily be seen that a smooth finished closure of this last ap is extremely important, both to the appearance and to the impermeability of the package. Further, a package having a poor closure of the folding elements under the final flap may be made attractive and be given a tight closure by a perfect closure of the top cover flap. To seal the cover flap to the carton, heat and pressure must be simultaneously applied to soften the thermoplastic and force the flap against the carton top to cause adherence. The cover ilap is of thin material, such as metallic foil, and is easily wrinkled or torn when the thermoplastic is soft, requiring a careful application of pressure, and the carton has walls which will easily buckle under stress thereby preventing the application of any sizeable forces from the end of the carton. The present invention takes into account these factors and accomplishes a smooth integral seal without damage to the carton.

Referring now to the sealing mechanism, and the accompanying closing machine, Figs. l and 4, the numeral 21 designates the ejector plate of the turret pocket which is carried on a rod 22 slidably carried by the turret and which is reciprocated by a rocker arm 15 pivoted by the action of a cam 17 The cam is constantly rotated by mechanism, not shown, to eject the carton from the machine each time the turret indexes a closed carton to Station D. The rod moves to the right by the action of the cam, when the pocket of the turret is in line with the deadboX 24 to push the carton from the turret pocket into the deadbox.

The dead box (Figs. 4 and 6) is a rectangular frame carried on a support 23 between the turret and sealing machine and in which the carton resides between the time when it has been ejected from the closing machine 4and when it will be moved into the sealing machine.

The height and width of the deadbox walls are the .same as the height andwidth of the carton so that the carton will be snugly held.

As the carton is pushed' into the deadbox, the cover flap lskimsunder an adjustable blade 25. (Fig. 4) which smooths the cover ap down dat on the top `of the carton. The blade is adjustably carried on a bracket 26. mounted on the deadbox, having a bolt 27. which extends through a vertical slot 28 in the blade. A pair of guide pins 29 on the bracket extends through vertical` slots 30 in the blade.

As the new carton is pushed into the deadbox from the turret, the preceding carton in the deadbox is pushed between the upper and lower spring holder arms 31 and 32 which hold the box on the inverter wheel 33. The forward edges of the deadbox, as well as the edges of the spring holder arms ofthe inverter wheel, are rounded (Fig. in order that the carton may easily pass without damaging the carton edges.

Referring to Fig. 6, .the safety switch ofthe deadbox is shown in detail.. If a misshapen, irregular or enlarged cartoncomes through, it would damage the sealer and the safety switch is provided to eliminate this danger. The side wall 34 of the deadbox is. carried on a pivotally mounted bell crank 35 and is held in upright position by a spring 36 connected between the arm and the support 23. An adjustablev stop bolt 37 in the arm strikes a lug 38 on the support and xes the upright position of the side wall. The. bolt is adjusteduntil the distance between the movable side wall 34 and the opposite fixed side wall 39 is equal to the width of the carton. A shoulder on the bell crank bears on the upper arm 4i) of ,a switch breaker bell crank 41, the lower arm 42 of which abuts the spring contact of a breaker switch 43. The switch, by means of electrical leads 44 to the power supply, completes the circuit to the driving motor, which is not shown.

`Should the closing, machine produce a misshapen, bent or over-sized carton as the carton enters the deadbox, it will force the movable wall 34 to the right, as shown in Fig. 6, causing the bell crank 35 to. pivot bell' crank 41 to open the switch contacts 43 and 4stop the drive motor, thereby preventing jamming and consequential damage to the machine.

The inverter wheel 33, as best shown in Figs. ll and 3, is carried on a horizontal shaft 45 journaled in frame pieces 46. The wheel is indexed through 90 each time a carton is inserted into the holders. The indexing of the wheel may be accomplished by conventional drive mechanism, such as a Geneva drive, which is synchronized with the delivery of the cartons from the closing machine. When used withY a turret type Lclosing machine, as shown, the intermittent drive` may b el taken from` the main turret and the inverter wheel will index each time the turret does.

An intermittently driven shaft48 is connected to the main turret drive or to a separate Geneva drive, not shown. Bevel` gear 560m shaft 48 drivesgear 58, vertical shaft 69 and bevel' gears 62 and 64, the latter being mounted on the inverter wheel shaft 45.

The inverter wheel, Figs. l, 3, and l2, is formed of radial spokes 66 which extend between the hub 68 on the shaft 45 and a rirn 70. The spring holders 31 and 32 of the inverter wheel are attached to the rim extending outwardly and are at an angle with the plane formed by the wheel, as will be seen in Fig. 12. The holders are resilient to hold they cartons firmly between them and the ends 72 are bent inwardly to form a Vholder pocket for the carton. The space between the spring vholders is slightly less than the height of the carton in order that the carton may be pressed therebetween while-it i's -being carried. This prevents the carton from falling from the inverter turret, holds the carton in proper shape preventing spilling of contents while inverting, and also holds the closing elements of thecartonin a closed position.

At the rear of the holder pockets, as viewed' in Fig. 3, is a smooth semi-circular shield 75 whichassists in holding the cartons in the pockets as'the inverter wheel rotates and prevents the cartons from being pushedcompletely through the pocketsfrom. the deadbox.

The inverter wheel shown in the preferred embodiment is provided with four ycarton carrying pockets. However, any convenient number may be used, providing the drive mechanism which indexes the wheel is so arranged that an empty pocket will be indexed in front of the vdeadbox for each delivery of a carton. In the present mechanism,

4 since four pockets are used, the wheel is indexed for each` carton` delivery.

After the carton has been indexed through two steps, or 180, so as to be diametrically opposite the deadbox, it will have been completely inverted with the unsealed flap facing downwardly.

To remove the container from the inverter pocket, a series of transfer pusher plates or paddles 76 (see Figs. l, 7, 8, l0, and ll) is transported on a chain 78 which is carried by a series of sprocket wheels 82, 84, 86, and S8. Laterally extending bars S0, secured to spaced links of the chain, support the plates. Four rectangularly arranged wheels 81 are attached to each bar and run in a guide track 89 (Figs. 7 and l1) to hold the plate vertical and normal to the chain in operation. The guide track runs only beneath the chain at its lower level where the pusher plates engage and transport the cartons. Chain sprocket 86 is mounted on a pivotal arm 90 having a slot 94 through whichpasses a stud 96 threaded into the frame. To adjust the chain to the proper tension, the arm is pivoted to the desired chain tension and there locked by tightening the stud. The chain is driven in timed relation to the inverter turret and the plates are so spaced that they will appear opposite a pocket on the inverter turret each time it is indexed, to pushthe carton out ofthe pocket.

As the plate contacts the face of' thecarton, Figs. 7, 8, and ll, the arrangement ofthe spring holders permits the lateral bars 80 to pass between them. The plate pushes the carton from between the spring holders over an intermediate supporting platform 91 and slides it over the heated sealing block 92.

It will be noticed `that the carton is positioned so that the ap extends rearward' with respect to the direction in which the carton is pushed, that is, the wall to which it is attached is the forward wall. The friction between the flap and the sealing platform exerts a tension on the iiap, drawing it rearwardly over the closing elements, keeping it flat and unwrinkled. This position .of the ap is shown in Fig. 9.

The sealing block is of metal, such as brass, and has a series of heating elements 93 mounted therein and evenly spaced for uniform heat. Leads 94 connect the elements to a source of electricity. The sealing platform has a slight depression the width of the carton which forms a channel 96 through which the carton slides. The sides of this channel have llets 98 which soften the box material and slightly round the edges of the box. The block temperature is chosen so that, during thetime of contact of the carton, the heat will penetrate the cover flap and soften the thermoplastic adhesive thereon but will not penetrate to the sealed underlying closure elements.

It will be noted that the box being inverted, the weight of the box and its contents bear against the iiap pressing it tightly against the carton top to create a smooth lamination between flap and carton.

To aid this action, a pressure plate 100 presses against the upper end or bottom` ofl the inverted carton. The plate is supported by pins 102 loosely carried in a frame piece 104. Nuts 105 threaded to the pins prevent them from pulling out of the frame piece and spiral compression springs 106 between the pressure plate and frame piece press the plate downwardly on the carton. The pressure plate exerts only a small pressure, auxiliary to the carton weight, as a semi-rigid` carton will buckle under excess pressure. This pressure on the carton, in addition to the. weight of the carton and contents, increases the friction which exists between the` heater block and the carton ap, pulling the closure flap smooth. The ap becomes soft and pliable with the softening of the adhesive and the weight of the carton and contents presses the flap smooth and squeezes the softened thermoplastic adhesive into the pores toy make a skin-tight, integral joint. Since the entire ap is in contact with the block, the other sealed elements are not disturbed by the action of sliding the inverted carton.

This pressure is continued as the carton is pushed over the heated sealing block and onto the lower pressure belt 108. A cooperating upper pressure `belt 110 causes the carton to be pressed tightly therebetween to maintain the integral joint between the flap and carton, while the thermoplastic is cooling.

The lower pressure belt is carried .by a driven roller 112 and an idler roller 114. An adjustableA idler roller 116 at a midpoint tensions the belt. Support idler rollers usare-arranged beneaththe-.beltfA to prevent sag-thereof from, the weight of the carton. Ehe rollersafjournaled between` twoV parallel.. frame` plates 120, which,f extend slightly yabovethe level ofl thebeltproviding guides for the-cartons.

The upper pressurebelt 110 passesover four rollers 122, 124, 126 and 128, rectangularly arranged, roller 122 being. driven. Roller- 1241is mounted-on-an adjustable shaft for purposes of adjusting theftensionof the belt. These rollers are also carried between', parallel'mounting plates 125. The drives for the chain 78fand-pressure beltslOS and 110 are illustrated inl-"iig, 9.

The arrangement ofthe sprockets and chains ,for-*driving, the pressure belts and transferA chains is shown-in Figs. 3 and 9, the chains being shown diagrammatically byalternate long and shortlines. The; main drive shaft 130l carriesa sprocket 132. Chainv 134'Y passes overy this sprocket and over sprocket 136'on-stub shaft 1'38,which carries the transfer chainvsproeket 82 to drive the transfer chain. The sprockets andfshafts are ljournaled on a-framc member 140. Atightener sprocket142'also engages thc chains, being mounted on carrying arm 144 on the frame member. A second sprocket 146 on they drive shaft 13,9 carries chain 148 which passesv over sprockets 150,- and 152 mounted on the shafts which carr-y pressure belt rollers 122 and 112 to drive the upper and lower pressure belts. A tightener sprocket 154 carriedon arm 156 also engages-the chain;

The driving mechanism isso-arrangedthat the.- belts travel at a faster linear' speedthan thechainl carrying the pusher plates. Therefore, when the car-ton is pushed to the end of the sealing platform and is caughtbetween the pressure belts, it begins movingA at a,A greater speed. The plates which stay behind the cartons during their entire travel between the pressurel belts. begin to drop back when the cartonsare picked up by thebeltsso that the distance between the plates and cartons` continually increases, leaving'a space between the cartonv and the plate when the carton reaches theends of the pressure belts.

This permits clearance between the heel of the transfer plate and the carton. As the chain passes over the end sprocket wheel 88 and they platey isv angularly swung around, the endof the sprocket brings the heel of the plate around, as is shown in Fig. 8. Provision ofl the clearance between the plate and thecarton prevents this heel from striking thef carton, and prevents. disturbance of the position of thecarton as it iscoolingbetween the pressure belts while the adhesive is still soft. Thishelps insure a tight seal between the flap andthecarton,

T he upper pressure belt does not extend quiteas, far to the right asthe lower, as shown in; Figs-9 andJlO,y to permit space-,for the paddles toy pass upwardly. When theV cartons haveV been sealed and: cooled andf reach the end of their travel along the lower pressure belt thef. drop off the belt to the right tovbe carried away by conveyor mechanisms which are not shown.

ltwill be noted from theplan view of'Fig. l2 that containers are delivered ata point which` lies directly in line with their path of delivery from ther top closing turret. This is accomplishedby placing the springholders 31 and 32, as described above, onthe inverter. to extend at an angle with the planeof the wheel 70, therebyv permitting the path of travel of the cartons through,l the :sealer and pressure belts to be at an angle to the path of the cartons when they are discharged from the closing machine. The two paths intersect. at. the, point of delivery of the sealed carton indicated bythe'arrow.

'lhe operation of the mechanism is believed clear from the foregoing explanation. However, a brief summary may be helpful in understanding'. the objectsl and principles of my invention.

Cartons which have been filled, but remain unclosed and unsealed, areinjectedinto. the pocket 13 of the turret 12 of the closing machine at station R. The turret is indexed to move the carton through a series of closing stations in the direction indicated by the arrows in Fig. 1. When the carton reaches station D, the closure elements will have been folded and sealed and the carton will be in the condition illustrated in Fig. 2, the top closure flap 16 requiring sealing to the top of the carton. As the turret indexes the carton to station D, the inverter wheel 33 simultaneously indexes a vacant holder pocket to a position opposite the deadbox 24. The closed carton is ejected from the turret and into the deadbox,

' 6 therebyvpushing,thefcartonfwhich previously rested. in the de adbox` into. the holder pocket. The. inverter` wheel s-rOtatedthr'ough 180 to turn the carton torarrupsidedown.y position. Atthat; pointapusher plate 76, carried downwardlyfon: its supportingchain 78, passesL between the; holder arms; `31and 32. on the inverter wheel as shown in Fig:v 8..l The platethus forces the carton out from between the holder arms, pushing it. over platform 91 onto the .heated sealingvblock.y 92 (Fig. 9). The weight of the carton and of its contents, combined with the auxiliaryl down-,ward'pressure applied by plate 100, press the top closing flap tightly to thecarton. The directionof movement issuch that the sidewall of the carton to which thejflap-is attached is forward. Therefore, the flap slidingion theheater block will `be drawn tightly back from itslline. of attachment, removing, wrinkles from the4 ap. The downwardpressureupon the flap, combined with the .slipping frictional action between the flapand the block, force the pliable ilap tightly against thek top` of the cartonover the other closure elements. The heat of the blocky has softened the thermoplastic adhesive and the pressure forces it. into the crevices and pores of the carton material, thereby obtaining an integral lamination between thev closure ap and carton top. As the carton continues to;- be pushed; by the plate 76, it is carried off the, sealingblock an'dbetween the upper. and lower sealinggbelts 110and108. The pressure sealing belts, aided by the weight of the, carton and contents, hold the closure iiap tightly against the carton until the thermoplastic adhesive cools and* solidies. The belts, traveling at a higher. speed than thepushery plates, cause an increasing apbetweenthe, plate and carton. As` the carton drops off they end of the lower belt, the pusher plate swings around the endsprocketSSfwithout strikingfthe carton.

Thus-it-wilLbe seen that l have provided ak successful mechanism` for sealing the overlapping flap to the. topl of acarton. rlhe mechanism is well suitedfor sealing carton apsconstructed. of. fragile and pliable materials whichY aregeasily crinkledor torn, such as metallic; foil. l have provided a device which will prevent distortion of theA shape of thev ap, both while the thermoplastic coat'- ing-l isy beingY heated and cooled, thereby obtaining an unimpregnable integral closure seal.

The-naechanism isespecially suited to closing cartons which have. side walls lack-ing rigidity because Vthe top closure ilap-can be sealed-.firmly against the carton with@ out-dangerofcollapsing the walls;

The device inverts the; carton` and seals they ap. without distrubing the sealed closure elements underneath andy yet forms. anextremely smooth closure which will beA attractive iny appearance, and. add'. substantial strength and increased impermeability to underlying closure ele# ments.

Whilethe invention is susceptible of various modifications` and; alternative constructions, l have shown in the drawingsA andthavetdcscribed in detail. the preferred embodiments. Hove/ever,` it is tobe understood that l do not thereby intend., to limit` theA invention to the specific form disclosed, butz intend to cover all-modifications and alternativeV constructions falling within the spirit and scope of therinvention as expressed in the appended claims.

Iv claim as my invention:

l. A machineforfsealing al closed carton comprising a mechanism for inverting-the carton, a closingplate having a ilatuppery surface, and transferral mechanism sliding the carton along said plate in itsinverted-position so that the weight of the carton bears against the closing flap.

2'. A` machine for sealing al closed carton comprising means to invert the carton, aat upwardly facing sur face over which the carton may be transported, a; trans-y ferral mechanism for sliding; thel carton in its inverted position over the surface4 with the weightl of the carton and'l itsv contents forcing ther closingY elements into sealing contact, and means for exerting. an auxiliary downward pressure: uponY the carton. as it is` being. movedl over said surface.

3. A machine for sealing a closed carton having an adhesive coated closing flap attached to a sidewall and overlying the folded closure elements, comprising means for inverting the carton to a position with the closing flap facing downwardly, a flat plate over which the carton may be slid, and means for transporting the carton in said position over the plate in a direction such that the friction between the flap and plate draws the closing flap over the closure elements.

4. A machine for sealing a filled and closed carton having adhesive coated closure elements folded over the contents comprising means for inverting the carton, means associated therewith for holding the closing elements in their folded'state preventing discharge of the contents while the carton is being inverted, a flat sealing surface over which the cartons may be slid, and means removing the carton from said holding means and sliding the carton over said surface, the weight of the contents compressing the closing elements.

5. A machine for sealing a lled carton having adhesive coated closure elements folded over the contents comprising means receiving the carton in an upright position, means for moving the carton through a semi-circular arc about a horizontal axis, a at surface positioned at the end of said arc, and a conveying device sliding the carton over said surface to seal the folded closure elements compressed by the weight of contents and carton into an integral closure.

6. A machine for sealing a carton having adhesive coated closure elements folded over the contents comprising an inverter element rotating about a horizontal axis and adapted to receive and hold a carton, means delivering the carton to the inverter, a supporting surface over which the carton may be slid, and mechanism adapted to remove the cartons from the inverter after it has been rotated to an inverted position and transport them over the supporting surface to compress the closure elements.

7. A machine for sealing a carton having adhesive coated closure elements folded over the contents comprising an inverting turret wheel rotating about a horizontal axis, spring holders peripherally mounted to extend outwardly and spaced to form carton receiving pockets between them, means inserting the carton between the holders in an upright position, a sealing plate having a flat upwardly facing surface, means forcing the carton from between said spring holders when the wheel has inverted the carton and sliding it over the sealing plate to seal the closure elements.

8. A machine for sealing a carton having folded closure elements and a thermoplastic adhesive coated closure flap overlying said elements comprising an inverter wheel having a carton holding pocket on the periphery and rotatable about a horizontal axis, means for inserting the closed carton into said pocket at one side of the wheel, a plate having a flat heated upwardly facing sealing surface on the other side of the wheel, means for removing the carton from the wheel and laterally pushing it over said sealing surface after the carton has been rotated through 180 to soften the thermoplastic adhesive and seal the closure flap over the closure elements.

9. A machine for sealing a closed carton having thermoplastic coated closure elements comprising means to invert the carton, a at upwardly facing heated sealing surface, means for sliding the carton in inverted position over said surface to soften the thermoplastic adhesive and compressibly seal the closure elements.

l0. A mechanism for sealing a closed carton having a thermoplastic adhesive coated ap overlying the closure elements comprising means for inverting the carton, means for holding the flap in overlying position while the carton is being inverted, a heated sealing surface over which the carton may be slid to soften the thermoplastic adhesive, means exerting a lateral pressure on the carton to move it over the sealing surface, and means exerting a downward pressure on the carton to force the flap and closure elements into integral relationship.

1l. A mechanism for sealing a closed carton formed of laminations of carton material and thermoplastic adhesive comprising means for inverting the carton, a heated sealing block having an upwardly facing channel through which the carton may be slid to soften the thermoplastic adhesive of the contacting carton surfaces, said channel having a flat bottom for contacting the carton top and having rounded sides for contacting and rounding the edges of the carton, and means to force the carton in inverted position through the channel.

12. A mechanism for sealing a carton top having thermoplastic coated closure elements, comprising in combination a sealing plate having a heated surface, pusher means for sliding the carton along the plate with the closure elements in Contact with the surface to soften the thermoplastic adhesive, a compression means for applying pressure to the closure elements while the thermoplastic hardens, and means for moving said compression means at a greater rate of speed than said pusher means.

13. A mechanism for sealing a container having thermoplastic coated closure elements comprising a heated sealing plate in a substantially horizontal position, a series of spaced pusher plates for pushing successive cartons in a path over the plate having their closure elements in sliding contact therewith, and spaced pressure belts positioned at the end of the plate to carry the cartons between them in said path and applying pressure thereto while the adhesive solidilies, and means for moving said belt at a greater rate of speed than said plates to space the cartons from the paddles.

14. A machine for sealing the top of a carton comprising an inverter turret rotatable about a horizontal axis and having a pair of holder arms extending outward from the turret spaced so as to form a carton pocket therebetween, means positioned beside the turret to insert a carton between the holder arms, a heated sealing plate positioned diametrically opposite the inserting means, and a paddle adapted to pass between the holder arms to push the carton from between the arms and over the heated plate to seal the carton top.

15. A machine for sealing a carton with thermoplastic ejected along a rst path from a closing machine, comprising an inverter turret carrying carton holders for receiving the carton from the closing machine, the turret being rotatable about an axis forming an angle with said first path, means for rotating the turret through 180 to invert the carton, a heated sealing plate, means for removing the carton from the turret and sliding it on end over the heated plate along a second path forming an angle with the turret axis, and means for applying pressure to the heated carton end while the adhesive cools, and carrying it along said second path to said rst path.

16. The method of sealing a closed carton having top closure elements coated with a thermoplastic adhesive which comprises inverting the carton, placing the inverted carton on a heated surface, and placing the carton in inverted position on an unheated surface until the thermoplastic adhesive solidies.

17. The method of sealing a closed carton having a flap connected to a side wall and overlying closure elements with a layer of thermoplastic adhesive therebetween, which comprises inverting the carton, sliding the carton across a heated surface with said ap-connected wall foremost to draw the iiap over the closure elements and press the flap to the closure elements, and removing the carton from the heated surface and pressing the flap to the carton until the adhesive cools.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,989,471 Belcher Jan. 29, 1935 1,991,223 Ledig et al. Feb. l2, 1935 2,206,761 Bergstein July 2, 1940 2,563,858 McGinley et al. Aug. 14, 1951 2,651,898 Kimball Sept. 15, 1953 

